APOD: NGC 1360: The Robin's Egg Nebula (2023 Aug 05)

[APOD Robot]

NGC 1360: The Robin's Egg Nebula

Explanation: This pretty nebula lies some 1,500 light-years away, its shape and color in this telescopic view reminiscent of a robin's egg. The cosmic cloud spans about 3 light-years, nestled securely within the boundaries of the southern constellation Fornax. Recognized as a planetary nebula, egg-shaped NGC 1360 doesn't represent a beginning though. Instead it corresponds to a brief and final phase in the evolution of an aging star. In fact, visible at the center of the nebula, the central star of NGC 1360 is known to be a binary star system likely consisting of two evolved white dwarf stars, less massive but much hotter than the Sun. Their intense and otherwise invisible ultraviolet radiation has stripped away electrons from the atoms in their mutually surrounding gaseous shroud. The predominant blue-green hue of NGC 1360 seen here is the strong emission produced as electrons recombine with doubly ionized oxygen atoms.

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[VictorBorun]

I wonder how can two stars in a binary system go together hot new white dwarfs

[Ann]

I wonder how can two stars in a binary system go together hot new white dwarfs

Orbiting white dwarfs. Illustration: NASA/Chandra X-ray Telescope

---

I guess they started out as a normal binary star, after which first one and then the other of the two "less than 8 solar masses components" used up their available fuel, shed their outer layers and became the "central double star" of a planetary nebula.

Now they orbit one another inside their common gaseous envelope. Soon the planetary nebula will disperse, and only the two orbiting white dwarfs will remain. If they are close enough, but only if they are close enough, their orbits may sink and they may eventually merge and create a supernova.

Ann

[Ann]

NGC 1360: The Robin's Egg Nebula. Image Credit & Copyright: Dong Liang

---

A robin's egg. Credit: Corey.

---

Yes, I guess the turquoise color of robin's eggs is a good proxy for the blue-green color of many planetary nebulas. A robin's egg is never likely to show any large patches of pink, however.

So why are robin's eggs blue?

(Victor, or someone, please help me - what is the hex code and RGB values for the lovely bluish cyan "robin's egg blue" large square that I just posted?)

Anyway. Why are robin's eggs blue?

The Spruce wrote:

The bile pigment biliverdin is responsible for blue tones in bird eggs, including robin's eggs. The color of an eggshell is determined by these pigments as they are deposited as the shell is formed in the shell gland.
...
Depending on the concentration of the bile pigment, the coloration can range from bright, bold blue or blue-green to pale ice blue and every shade in between.

A bright blue color of the egg may suggest to the male robin that the chick inside is in good health, and the male is more likely to spend more time feeding chicks hatched from brightly colored eggs. And blue-green eggs may protect the chicks inside from the harmful effects of sunlight.

Click to play embedded YouTube video.

Ann

[VictorBorun]

I guess they started out as a normal binary star, after which first one and then the other of the two "less than 8 solar masses components" used up their available fuel, shed their outer layers and became the "central double star" of a planetary nebula.
Ann

what are the chances for two blue giants in a binary to burn for say 100 million years and then go white dwarf in the same say thousand years?

[VictorBorun]

A robin's egg is never likely to show any large patches of pink, however.
Ann

the alien conspirator who went 1500 years back in time and 1500 ly away to create the Robin's Egg Nebula got somewhat confused:

they correctly understood the phrase

your eyes were bluer then robin's eggs

but failed to see that malinovka's (robin's) eggs are not malinovy (magenta)

[Ann]

I guess they started out as a normal binary star, after which first one and then the other of the two "less than 8 solar masses components" used up their available fuel, shed their outer layers and became the "central double star" of a planetary nebula.
Ann

what are the chances for two blue giants in a binary to burn for say 100 million years and then go white dwarf in the same say thousand years?

They don't have to go white dwarfs within the same millennium.

Consider Sirius:

Sirius A with its white dwarf companion, Sirius B (lower left.) Credit: NASA, ESA, H. Bond (STScI), and M. Barstow (University of Leicester)

---

Wikipedia wrote:

Sirius is a binary star consisting of a main-sequence star of spectral type A0 or A1, termed Sirius A, and a faint white dwarf companion of spectral type DA2, termed Sirius B.
...
The system is between 200 and 300 million years old.[13] It was originally composed of two bright bluish stars. The initially more massive of these, Sirius B, consumed its hydrogen fuel and became a red giant before shedding its outer layers and collapsing into its current state as a white dwarf around 120 million years ago.

Sirius A is also going to become a white dwarf eventually. My amateur guess is that it will take at least 200 million years for that to happen. That's because Sirius A must first deplete its core hydrogen, then turn into a red giant, then run through its red giant life time which will include a strongly shrinking core and an enormous swelling and cooling of its outer layers, then a helium flash followed by core helium fusion, then helium depletion in its core and a new swelling and a general instability caused by on-again, off-again shell hydrogen and shell helium burning, and then, finally, a shedding of its outer layers and the birth of a new planetary nebula and a new white dwarf.

But this is my point. At the time when Sirius A becomes a white dwarf, Sirius B will still be a white dwarf orbiting their common center of mass.

And the planetary nebula that will be created by Sirius A will envelop Sirius B, too. So that's what Sirius will become for a short time in the future, a binary white dwarf inside a common-envelope planetary nebula.

Ann

[VictorBorun]

At the time when Sirius A becomes a white dwarf, Sirius B will still be a white dwarf orbiting their common center of mass.
And the planetary nebula that will be created by Sirius A will envelop Sirius B, too. So that's what Sirius will become for a short time in the future, a binary white dwarf inside a common-envelope planetary nebula.
Ann

so two evolved white dwarf stars may be out of sync after all, one is a 100 million years colder white dwarf than the other?

[Chris Peterson]

At the time when Sirius A becomes a white dwarf, Sirius B will still be a white dwarf orbiting their common center of mass.
And the planetary nebula that will be created by Sirius A will envelop Sirius B, too. So that's what Sirius will become for a short time in the future, a binary white dwarf inside a common-envelope planetary nebula.
Ann

so two evolved white dwarf stars may be out of sync after all, one is a 100 million years colder white dwarf than the other?

Sure, why not? (A white dwarf cools insignificantly in 100 million years, of course.)

[Roy]

Interesting comparison to Sirius A&B. NGC1360 masses are given as .555 and .679 solar mass. Do they have an orbital period? Otherwise how are these estimated? ( Sirius A 2.063, B 1.018 solar masses, 50 year period elliptical orbit, approximately from .5 AU inside Saturn’s orbit to 4.5 AU outside Neptune’s orbit)

[Ann]

NGC 1360: The Robin's Egg Nebula. Image Credit & Copyright: Dong Liang

---

A robin's egg. Credit: Corey.

---

Yes, I guess the turquoise color of robin's eggs is a good proxy for the blue-green color of many planetary nebulas. A robin's egg is never likely to show any large patches of pink, however.

So why are robin's eggs blue?

(Victor, or someone, please help me - what is the hex code and RGB values for the lovely bluish cyan "robin's egg blue" large square that I just posted?)

Ann

Sorry for quoting myself, but no one was interested in helping me try to find a hex code for the bluish cyan large rectangle in my first post.

Maybe this is the correct color? ██████ What do you think?

Its hex code is #00A8C9, and as for its RGB value, there is clearly not a lot of red in it (if any), and there is more blue than green in it.

Maybe it's a bit like the hue corresponding to 482 nm, which looks like this: ██████

The RGB value of 482 nm is R=0. G=222 and B=255. But my first rectangle is obviously darker than the color sample I posted just now.

Ann

[johnnydeep]

NGC 1360: The Robin's Egg Nebula. Image Credit & Copyright: Dong Liang

---

A robin's egg. Credit: Corey.

---

Yes, I guess the turquoise color of robin's eggs is a good proxy for the blue-green color of many planetary nebulas. A robin's egg is never likely to show any large patches of pink, however.

So why are robin's eggs blue?

(Victor, or someone, please help me - what is the hex code and RGB values for the lovely bluish cyan "robin's egg blue" large square that I just posted?)

Ann

Sorry for quoting myself, but no one was interested in helping me try to find a hex code for the bluish cyan large rectangle in my first post.

Maybe this is the correct color? ██████ What do you think?

Its hex code is #00A8C9, and as for its RGB value, there is clearly not a lot of red in it (if any), and there is more blue than green in it.

Maybe it's a bit like the hue corresponding to 482 nm, which looks like this: ██████

The RGB value of 482 nm is R=0. G=222 and B=255. But my first rectangle is obviously darker than the color sample I posted just now.

Ann

Gimp tells me that the RGB of the pixels in your first post is:

robins egg blue pixel rgb.jpg (12.33 KiB) Viewed 5408 times

But what "A" is I'm not too sure. I suck at using Gimp. It's COMPLETELY unintuitive to me!

[orin stepanek]

Robin's egg! My dad loved the color for paint; why? I don't know! It
is a pretty color though! Maybe Robins were helping the easter
bunny! I think I've seen some black ones though!

NGC1360; largest robin egg of all time!

[Ann]

NGC 1360: The Robin's Egg Nebula. Image Credit & Copyright: Dong Liang

---

A robin's egg. Credit: Corey.

---

Yes, I guess the turquoise color of robin's eggs is a good proxy for the blue-green color of many planetary nebulas. A robin's egg is never likely to show any large patches of pink, however.

So why are robin's eggs blue?

(Victor, or someone, please help me - what is the hex code and RGB values for the lovely bluish cyan "robin's egg blue" large square that I just posted?)

Ann

Sorry for quoting myself, but no one was interested in helping me try to find a hex code for the bluish cyan large rectangle in my first post.

Maybe this is the correct color? ██████ What do you think?

Its hex code is #00A8C9, and as for its RGB value, there is clearly not a lot of red in it (if any), and there is more blue than green in it.

Maybe it's a bit like the hue corresponding to 482 nm, which looks like this: ██████

The RGB value of 482 nm is R=0. G=222 and B=255. But my first rectangle is obviously darker than the color sample I posted just now.

Ann

Gimp tells me that the RGB of the pixels in your first post is:


robins egg blue pixel rgb.jpg


But what "A" is I'm not too sure. I suck at using Gimp. It's COMPLETELY unintuitive to me!

Fantastic, Johnny! That's amazing! Gimp, what's that? I've never heard of it.

It's so interesting that there was a bit of red in the large cyan square I posted. But in the "color sample" at 482 nm, there was no red. Can you tell the presence of red from the fact that the large square I posted is darker than the "482 nm" strip?

Ann

[johnnydeep]

Sorry for quoting myself, but no one was interested in helping me try to find a hex code for the bluish cyan large rectangle in my first post.

Maybe this is the correct color? ██████ What do you think?

Its hex code is #00A8C9, and as for its RGB value, there is clearly not a lot of red in it (if any), and there is more blue than green in it.

Maybe it's a bit like the hue corresponding to 482 nm, which looks like this: ██████

The RGB value of 482 nm is R=0. G=222 and B=255. But my first rectangle is obviously darker than the color sample I posted just now.

Ann

Gimp tells me that the RGB of the pixels in your first post is:


robins egg blue pixel rgb.jpg


But what "A" is I'm not too sure. I suck at using Gimp. It's COMPLETELY unintuitive to me!

Fantastic, Johnny! That's amazing! Gimp, what's that? I've never heard of it.

It's so interesting that there was a bit of red in the large cyan square I posted. But in the "color sample" at 482 nm, there was no red. Can you tell the presence of red from the fact that the large square I posted is darker than the "482 nm" strip?

Ann

Gimp is a free image processing and manipulation program available for Windows, Mac and Linux:

GIMP (/ɡɪmp/ GHIMP; GNU Image Manipulation Program) is a free and open-source raster graphics editor[4] used for image manipulation (retouching) and image editing, free-form drawing, transcoding between different image file formats, and more specialized tasks. It is not designed to be used for drawing, though some artists and creators have used it in this way.[5]

GIMP is released under the GPL-3.0-or-later license and is available for Linux, macOS, and Microsoft Windows.[6]

[Ann]

Delete, please.

Ann

[Ann]

Gimp tells me that the RGB of the pixels in your first post is:


robins egg blue pixel rgb.jpg


But what "A" is I'm not too sure. I suck at using Gimp. It's COMPLETELY unintuitive to me!

Fantastic, Johnny! That's amazing! Gimp, what's that? I've never heard of it.

It's so interesting that there was a bit of red in the large cyan square I posted. But in the "color sample" at 482 nm, there was no red. Can you tell the presence of red from the fact that the large square I posted is darker than the "482 nm" strip?

Ann

Gimp is a free image processing and manipulation program available for Windows, Mac and Linux:

GIMP (/ɡɪmp/ GHIMP; GNU Image Manipulation Program) is a free and open-source raster graphics editor[4] used for image manipulation (retouching) and image editing, free-form drawing, transcoding between different image file formats, and more specialized tasks. It is not designed to be used for drawing, though some artists and creators have used it in this way.[5]

GIMP is released under the GPL-3.0-or-later license and is available for Linux, macOS, and Microsoft Windows.[6]

Huh. I'd need someone to help me install it, and then someone to show me how to use it. Primarily for finding out about the exact color of an image, or more likely, of parts of an image.

Don't know if I can do that, so is it okay if I ask you again, Johnny?

Ann

[Chris Peterson]

Yes, I guess the turquoise color of robin's eggs is a good proxy for the blue-green color of many planetary nebulas. A robin's egg is never likely to show any large patches of pink, however.

Guess you've never seen a robin's nest after a hawk or jay got to it...

[johnnydeep]

Fantastic, Johnny! That's amazing! Gimp, what's that? I've never heard of it.

It's so interesting that there was a bit of red in the large cyan square I posted. But in the "color sample" at 482 nm, there was no red. Can you tell the presence of red from the fact that the large square I posted is darker than the "482 nm" strip?

Ann

Gimp is a free image processing and manipulation program available for Windows, Mac and Linux:

GIMP (/ɡɪmp/ GHIMP; GNU Image Manipulation Program) is a free and open-source raster graphics editor[4] used for image manipulation (retouching) and image editing, free-form drawing, transcoding between different image file formats, and more specialized tasks. It is not designed to be used for drawing, though some artists and creators have used it in this way.[5]

GIMP is released under the GPL-3.0-or-later license and is available for Linux, macOS, and Microsoft Windows.[6]

Huh. I'd need someone to help me install it, and then someone to show me how to use it. Primarily for finding out about the exact color of an image, or more likely, of parts of an image.

Don't know if I can do that, so is it okay if I ask you again, Johnny?

Ann

Does this work for you - https://www.colorcodepicker.com ? You just upload an image and you can then move your mouse over it and it displays the RGB values.

[Chris Peterson]

Fantastic, Johnny! That's amazing! Gimp, what's that? I've never heard of it.

It's so interesting that there was a bit of red in the large cyan square I posted. But in the "color sample" at 482 nm, there was no red. Can you tell the presence of red from the fact that the large square I posted is darker than the "482 nm" strip?

Ann

Gimp is a free image processing and manipulation program available for Windows, Mac and Linux:

GIMP (/ɡɪmp/ GHIMP; GNU Image Manipulation Program) is a free and open-source raster graphics editor[4] used for image manipulation (retouching) and image editing, free-form drawing, transcoding between different image file formats, and more specialized tasks. It is not designed to be used for drawing, though some artists and creators have used it in this way.[5]

GIMP is released under the GPL-3.0-or-later license and is available for Linux, macOS, and Microsoft Windows.[6]

Huh. I'd need someone to help me install it, and then someone to show me how to use it. Primarily for finding out about the exact color of an image, or more likely, of parts of an image.

Don't know if I can do that, so is it okay if I ask you again, Johnny?

Ann

Just download Microsoft Power Toys. It installs a few simple utilities, one of which lets you point at anything on your screen and get a readout of the RGB values.

[Roy]

Interesting comparison to Sirius A&B. NGC1360 masses are given as .555 and .679 solar mass. Do they have an orbital period? Otherwise how are these estimated? ( Sirius A 2.063, B 1.018 solar masses, 50 year period elliptical orbit, approximately from .5 AU inside Saturn’s orbit to 4.5 AU outside Neptune’s orbit)

OK, I looked up binary-mass function in Wikipedia, so there must have been a reading on period from something. But without knowing inclination of orbit, elliptical estimation, and so on mass of the two stars (if indeed there are only two) is, at this distance and obscurity a SWAG.

[johnnydeep]

Gimp is a free image processing and manipulation program available for Windows, Mac and Linux:

Huh. I'd need someone to help me install it, and then someone to show me how to use it. Primarily for finding out about the exact color of an image, or more likely, of parts of an image.

Don't know if I can do that, so is it okay if I ask you again, Johnny?

Ann

Just download Microsoft Power Toys. It installs a few simple utilities, one of which lets you point at anything on your screen and get a readout of the RGB values.

Nice - thanks. I can't believe I didn't know about this pack of tools before now. And here it is in action, after picking Ann's color:

[VictorBorun]

NGC 1360: The Robin's Egg Nebula. Image Credit & Copyright: Dong Liang

---

A robin's egg. Credit: Corey.

---

Yes, I guess the turquoise color of robin's eggs is a good proxy for the blue-green color of many planetary nebulas. A robin's egg is never likely to show any large patches of pink, however.

So why are robin's eggs blue?

(Victor, or someone, please help me - what is the hex code and RGB values for the lovely bluish cyan "robin's egg blue" large square that I just posted?)

Ann

Sorry for quoting myself, but no one was interested in helping me try to find a hex code for the bluish cyan large rectangle in my first post.

Maybe this is the correct color? ██████ What do you think?

Its hex code is #00A8C9, and as for its RGB value, there is clearly not a lot of red in it (if any), and there is more blue than green in it.

Maybe it's a bit like the hue corresponding to 482 nm, which looks like this: ██████

The RGB value of 482 nm is R=0. G=222 and B=255. But my first rectangle is obviously darker than the color sample I posted just now.

Ann

neither the Robin's Egg Nebula nor a robin's egg have a colour hue or a wavelength.
Both look like some indigo ink that thickens white to pale cyan to blue to dark violet to black.
Here is a slice from this APOD

GC 1360-The Robin's Egg Nebula (2023 Aug 05) -.jpg (991 Bytes) Viewed 5330 times

[Chris Peterson]

neither the Robin's Egg Nebula nor a robin's egg have a colour hue or a wavelength.
Both look like some indigo ink that thickens white to pale cyan to blue to dark violet to black.

The egg shell has a pretty uniform hue. The image of the egg does not because of the intensity variations. Even with a hue created by a very narrow wavelength, there is no single color (or meaningful RGB representation) because the actual color is defined by intensity as well as hue.

[VictorBorun]

neither the Robin's Egg Nebula nor a robin's egg have a colour hue or a wavelength.
Both look like some indigo ink that thickens white to pale cyan to blue to dark violet to black.

The egg shell has a pretty uniform hue. The image of the egg does not because of the intensity variations. Even with a hue created by a very narrow wavelength, there is no single color (or meaningful RGB representation) because the actual color is defined by intensity as well as hue.

here's a fragment of the pic of a robin's egg

Robin's Egg-.jpg (1.62 KiB) Viewed 5309 times

You can see that a point of the sun's reflection is white; here the random movement of a photon scattered by CaCO₂ crystallites is minimal and chances for an ink molecule to absorb that photon is minimal.
The wider the angle from the sun's reflection the greater is the distance a typical photon travels through the egg's shell material before coming out along your line of sight. That is exactly what thickening a dye means.

There's a limit to that thickening here: a robin's egg has a thin shell with a budget quantity of ink and just white matter beneath.
So the longest travellers among photons get to pass through the shell and scatter from the white.
You can see just white to pale cyan to cyan-blue, no blue to dark violet to black